Hydraulic parking brake system for railway vehicles

Abstract

A parking brake system for use on a railway car includes an actuator which is adapted to be attached to a service brake actuating lever arm of the railway car and to receive a flow of non-compressible holding liquid from a reservoir through a first valve unit. The first valve unit permits the liquid to freely flow to and from the actuator in a first position and only permits flow of the liquid towards the actuator in a second position. With this arrangement, movement of the service brake actuating lever arm automatically causes the actuator to be supplied with holding liquid from the reservoir, which liquid can be selectively retained by shifting of the first valve unit to the second position. Furthermore in accordance with the invention, the actuator can be shifted by supplying pressurized holding liquid thereto through the use of a motor driven pump circuit including a pressurizable reservoir. In accordance with this embodiment of the invention, an additional valve is provided between the pressurizable reservoir and the actuator to selectively interconnect the pressurizable reservoir to the actuator. Various components of the system are preferably integrated into units which can then be interconnected. With such an arrangement, only minor attachments have to be made to retrofit an existing railway car with the parking brake system. Furthermore, the system can be incorporated in either static or pressurized modes of operation with the static system being readily convertible to a pressurized system.

We claim: 
     
       1. A railway car parking brake system comprising: an actuator including a piston, cylinder, and an actuator rod, said piston being movably mounted within said cylinder so as to divide said cylinder into at least first and second chambers, said actuator rod having a first end portion secured to said piston for movement between extended and retracted positions and a second end portion that extends from said cylinder, one of said cylinder and the second end portion of said actuator rod being adapted to be attached to a support portion of a railway car and the other of said cylinder and the second end portion of said actuator rod being adapted to be attached to a movable railway car service brake actuating member such that movement of said piston relative to said cylinder will shift the movable railway car service brake actuating member relative to the support portion of the railway car;   a reservoir adapted to house a supply of liquid;   a conduit system fluidly interconnecting said reservoir to the first chamber of said cylinder; and   at least one valve member interposed within said conduit system between said reservoir and the first chamber of said cylinder for controlling liquid flow through said conduit system, said valve member including a one-way valve arranged to continuously block liquid flow out of the first chamber towards the reservoir while permitting flow of liquid into the first chamber from the reservoir.   
     
     
       2. The railway car parking brake system as claimed in claim 1, wherein at least said linear actuator and said reservoir are integrated into a single unit. 
     
     
       3. The railway car parking brake system as claimed in claim 2, wherein said single unit comprises a unitary housing provided with a pair of spaced bores, one of which defines said cylinder and the other of which defines said reservoir. 
     
     
       4. The railway car parking brake system as claimed in claim 2, wherein said reservoir is concentrically mounted about said cylinder. 
     
     
       5. The railway car parking brake system as claimed in claim 2, wherein said single unit includes first and second end cap members between which said cylinder and said reservoir extend. 
     
     
       6. The railway car parking brake system as claimed in claim 5, further comprising a port extending from said reservoir through one of said first and second end cap members for at least one of filling and draining of said reservoir. 
     
     
       7. The railway car parking brake system as claimed in claim 5, wherein said single unit further comprises a plurality of circumferentially spaced tie rods interconnecting said first and second end cap members. 
     
     
       8. The railway car parking brake system as claimed in claim 5, wherein at least a portion of said conduit system is formed within said first end cap member. 
     
     
       9. The railway car parking brake system as claimed in claim 8, wherein said reservoir includes an internal piston which divides said reservoir into first and second chambers, said conduit system being open to the first chamber of said reservoir through said first end cap member, the second chamber of said reservoir being vented to atmosphere. 
     
     
       10. The railway car parking brake system as claimed in claim 1, wherein said reservoir includes an internal piston which divides said reservoir into first and second chambers, said conduit system being open to the first chamber of said reservoir and the second chamber of said reservoir being vented to atmosphere. 
     
     
       11. The railway car parking brake system as claimed in claim 1, wherein said valve member is also arranged to selectively permit the supply of liquid in the reservoir to be drawn into the first chamber of said cylinder and returned to the reservoir by the movement of the piston within said cylinder. 
     
     
       12. The railway car parking brake system as claimed in claim 1, further comprising a venting passage opening the second chamber of said cylinder to atmosphere. 
     
     
       13. The railway car parking brake system as claimed in claim 1, wherein said at least one valve member includes a flow control valve adapted to be selectively shifted to an open position wherein liquid is free to flow to and from the first chamber of said cylinder and a closed, flow-through preventing position. 
     
     
       14. The railway car parking brake system as claimed in claim 13, wherein said one-way valve comprises a check valve. 
     
     
       15. The railway car parking brake system as claimed in claim 13, wherein said flow control valve comprises a manually actuated valve. 
     
     
       16. The railway car parking brake system as claimed in claim 1, further comprising: a pump having an input in fluid communication with said reservoir and an output in fluid communication with said first chamber of said cylinder, said one-way valve located between said pump and said first chamber.   
     
     
       17. The railway car parking brake system as claimed in claim 16, further comprising a second pressurized reservoir connected to the output side of said pump, a pressure relief valve, responsive to sensed pressure of liquid delivered to said second reservoir from said pump, arranged parallel to said second reservoir for diverting a flow of liquid from said pump to the first recited reservoir. 
     
     
       18. The railway car parking brake system as claimed in claim 17, wherein both reservoirs are integrated into a single unit. 
     
     
       19. The railway car parking brake system as claimed in claim 18, wherein said single unit includes first and second end cap members between which said both reservoirs are mounted. 
     
     
       20. The railway car parking brake system as claimed in claim 19, wherein said first end cap member is formed with a plurality of internal conduits terminating at mounting ports. 
     
     
       21. The railway car parking brake system as claimed in claim 20, including a motor drivingly connected to said pump and wherein said pump and said motor are integrated into a single unit. 
     
     
       22. The railway car parking brake system as claimed in claim 21, wherein said pump and said motor are interconnected through a mounting block, said mounting block being adapted to be interconnected to said first end cap member such that said reservoirs, said pump and said motor form a single assembly. 
     
     
       23. The railway car parking brake system as claimed in claim 17, further comprising a motor drivingly connected to said pump; and a pressure-sensitive switch in fluid communication to said second reservoir, said switch being electrically connected to said motor such that said motor is automatically activated to drive said pump when a sensed pressure in said second reservoir is below a predetermined level. 
     
     
       24. The railway car parking brake system as claimed in claim 23, wherein said at least one valve member includes a flow control valve adapted to be shifted to an open position wherein liquid is free to flow to and from the first chamber of said cylinder and a closed, flow-through preventing position and wherein said one-way valve is arranged in parallel to said flow control valve. 
     
     
       25. The railway car parking brake system as claimed in claim 24, wherein said at least one valve member includes a third valve arranged between said pump and said actuator in series with said flow control valve, said third valve being movable between a first position wherein the first chamber of said cylinder is open to said first recited reservoir and a second position wherein the output of said pump is open to said flow control valve. 
     
     
       26. The railway car parking brake system as claimed in claim 25, further comprising an element for biasing said third valve towards said first position. 
     
     
       27. A railway car parking brake system comprising: an actuator including a piston, cylinder, and an actuator rod, said piston being movably mounted within said cylinder so as to divide said cylinder into at least first and second chambers, said actuator rod having a first end position secured to said piston for movement between extended and retracted positions and a second end portion that extends from said cylinder, one of said cylinder and the second end portion of said actuator rod being adapted to be attached to a support portion of a railway car and the other of said cylinder and the second end portion of said actuator rod being adapted to be attached to a movable railway car service brake actuating member such that movement of said piston relative to said cylinder will shift the movable railway car service brake actuating member relative to the support portion of the railway car;   a first reservoir adapted to house a supply of holding liquid;   a conduit system fluidly interconnecting said first reservoir to the first chamber of said cylinder; and   a valve unit interposed within said conduit system between said first reservoir and the first chamber of said cylinder, said valve unit being adjustable between a first position wherein holding liquid can freely flow between the first chamber of said cylinder and the reservoir and a second position wherein holding liquid can only flow from said first reservoir towards the first chamber of said cylinder and not in a reverse direction.   
     
     
       28. The railway car parking brake system as claimed in claim 27, further comprising a venting passage opening the second chamber of said cylinder to atmosphere. 
     
     
       29. The railway car parking brake system as claimed in claim 27, wherein said first reservoir and said cylinder are integrated into a single unit. 
     
     
       30. The railway car parking brake system as claimed in claim 29, wherein said single unit includes first and second end cap members between which said first reservoir and said cylinder extend, said first and second end cap members being interconnected by a plurality of tie members, at least a portion of said conduit system being formed in said first end cap member. 
     
     
       31. The railway car parking brake system as claimed in claim 27, further comprising: a second pressurizable reservoir for storing a quantity of holding liquid;   a pump having an input in fluid communication with said first reservoir and an output in fluid communication with said second reservoir; and   drive means connected to said pump wherein operation of said drive means causes holding liquid to be drawn from said first reservoir and delivered to said second reservoir to pressurize said second reservoir.   
     
     
       32. The railway car parking brake system as claimed in claim 31, further comprising a pressure-sensitive switch in fluid communication to said second reservoir, said switch being electrically connected to said drive means such that said drive means is automatically activated to drive said pump when a sensed pressure in said second reservoir is below a predetermined level. 
     
     
       33. The railway car parking brake system as claimed in claim 31, wherein said valve unit includes a flow control valve adapted to be shifted to an open position wherein liquid is free to flow to and from the first chamber of said cylinder and a closed, flow-through preventing position and a second one-way valve, said one-way valve being arranged in parallel to said flow control valve, said one-way valve only permitting uni-directional flow of liquid towards said first chamber therethrough. 
     
     
       34. The railway car parking brake system as claimed in claim 33, further comprising a third valve arranged between said pump and said actuator in series with said flow control valve, said third valve being movable between a first position wherein the first chamber of said cylinder is open to said reservoir and a second position wherein the output of said pump is open to said flow control valve. 
     
     
       35. The railway car parking brake system as claimed in claim 31, wherein said first and second reservoirs are integrated into a single unit. 
     
     
       36. The railway car parking brake system as claimed in claim 35, wherein said single unit includes first and second end cap members between which said first and second reservoirs are mounted, said first end cap member being formed with a plurality of internal conduits terminating at mounting ports. 
     
     
       37. The railway car parking brake system as claimed in claim 36, wherein said pump and said drive means are interconnected through a mounting block, said mounting block being adapted to be interconnected to said first end cap member such that said reservoirs, said pump and said drive means form a single assembly. 
     
     
       38. A method of holding a service brake system on a railway car in a desired brake setting position comprising: interconnecting a linear actuator, including a cylinder having a piston movable therein which divides said cylinder into first and second chambers and a rod attached to said piston, between a body portion of the railway car and a lever which is shiftable by the service brake system;   connecting a holding liquid reservoir to the first chamber of said linear actuator through a holding liquid filled conduit;   interposing a one-way valve between said linear actuator and said reservoir; and   continuously blocking flow of holding liquid out of the first chamber toward the reservoir while continuously permitting flow of holding liquid into the first chamber through said one-way valve as a result of piston motion in a direction enlarging said first chamber.   
     
     
       39. The method of holding a service brake system as claimed in claim 38, further comprising: incorporating at least said linear actuator and said reservoir into a unitary assembly. 
     
     
       40. The method of holding a service brake system as claimed in claim 38, further comprising: pressurizing a holding liquid pressurizable reservoir by supplying liquid thereto from a pump which draws liquid from a holding liquid reservoir;   interposing a second valve, in series with said one-way valve, between said pressurizable reservoir and said first chamber of said cylinder; and   controlling the operation of the pump in response to sensed pressure at the pressurizable reservoir.   
     
     
       41. The method of holding a service brake system as claimed in claim 40, further comprising: biasing said second valve towards a position which prevents the flow of liquid from the pressurizable reservoir to the first chamber of the cylinder. 
     
     
       42. A railway car parking brake system comprising: an actuator including a piston, cylinder, and an actuator rod, said piston being movably mounted within said cylinder so as to divide said cylinder into at least first and second chambers, said actuator rod having a first end portion secured to said piston for movement between extended and retracted positions and a second end portion that extends from said cylinder, one of said cylinder and the second end portion of said actuator rod being adapted to be attached to a support portion of a railway car and the other of said cylinder and the second end portion of said actuator rod being adapted to be attached to a movable railway car service brake actuating member such that movement of said piston relative to said cylinder will shift the movable railway car service brake actuating member relative to the support portion of the railway car;   a reservoir adapted to house a supply of liquid;   a conduit system fluidly interconnecting said reservoir to the first chamber of said cylinder; and   at least one valve member interposed within said conduit system between said reservoir and the first chamber of said cylinder for controlling liquid flow through said conduit system;   wherein said reservoir includes an internal piston which divides said reservoir into first and second chambers, said conduit system being open to the first chamber of said reservoir and the second chamber of said reservoir being vented to atmosphere.   
     
     
       43. The railway car parking brake system as claimed in claim 42, wherein the supply of liquid in the reservoir is drawn into the first chamber of said cylinder and returned to the reservoir by the movement of the piston within said cylinder. 
     
     
       44. A railway car parking brake system comprising: an actuator including a piston, cylinder, and an actuator rod, said piston being movably mounted within said cylinder so as to divide said cylinder into at least first and second chambers, said actuator rod having a first end portion secured to said piston for movement between extended and retracted positions and a second end portion that extends from said cylinder, one of said cylinder and the second end portion of said actuator rod being adapted to be attached to a support portion of a railway car and the other of said cylinder and the second end portion of said actuator rod being adapted to be attached to a movable railway car service brake actuating member such that movement of said piston relative to said cylinder will shift the movable railway car service brake actuating member relative to the support portion of the railway car;   a reservoir adapted to house a supply of liquid;   a conduit system fluidly interconnecting said reservoir to the first chamber of said cylinder; and   at least one valve member interposed within said conduit system between said reservoir and the first chamber of said cylinder for controlling liquid flow through said conduit system; and   a venting passage opening the second chamber of said cylinder to atmosphere.   
     
     
       45. A railway car parking brake system comprising: an actuator including a piston, cylinder, and an actuator rod, said piston being movably mounted within said cylinder so as to divide said cylinder into at least first and second chambers, said actuator rod having a first end portion secured to said piston for movement between extended and retracted positions and a second end portion that extends from said cylinder, one of said cylinder and the second end portion of said actuator rod being adapted to be attached to a support portion of a railway car and the other of said cylinder and the second end portion of said actuator rod being adapted to be attached to a movable railway car service brake actuating member such that movement of said piston relative to said cylinder will shift the movable railway car service brake actuating member relative to the support portion of the railway car;   a reservoir adapted to house a supply of liquid;   a conduit system fluidly interconnecting said reservoir to the first chamber of said cylinder; and   at least one valve member interposed within said conduit system between said reservoir and the first chamber of said cylinder for controlling liquid flow through said conduit system;   wherein said at least one valve member includes a first valve adapted to be shifted to an open position wherein liquid is free to flow to and from the first chamber of said cylinder and a closed, flow-through preventing position and a second valve, said second valve being arranged in parallel to said first valve, said second valve always permitting unidirectional flow of liquid towards said first chamber therethrough.   
     
     
       46. The method according to claim 38, including continuously venting said second chamber to atmosphere. 
     
     
       47. A method of holding a service brake system on a railway car in a desired brake setting position comprising: interconnecting a linear actuator, including a cylinder having a piston movable therein which divides said cylinder into first and second chambers and a rod attached to said piston, between a body portion of the railway car and a lever which is shiftable by the service brake system;   connecting a holding liquid reservoir to the first chamber of said linear actuator through a holding liquid filled conduit;   interposing a one-way valve between said linear actuator and said reservoir; and   continuously blocking flow of holding liquid out of the first chamber toward the reservoir while continuously permitting flow of holding liquid into the first chamber through said one-way valve, including selectively pumping pressurized holding liquid from the reservoir to the first chamber through said one-way valve to actuate said lever towards a brake setting position with the pump located between the one-way valve and the reservoir.   
     
     
       48. The method according to claim 47, including selectively enabling free flow of holding liquid between said reservoir and said first chamber in parallel with said one-way valve. 
     
     
       49. The method according to claim 47, including continuously venting said second chamber to atmosphere. 
     
     
       50. The method according to claim 48, including continuously venting said second chamber to atmosphere.